Pressure regulation via pump control for exhaust system

ABSTRACT

A control system for a pump in a vehicle exhaust system includes a pump having an inlet port and an outlet port, a fluid supply in fluid communication with the inlet port, and a supply line in fluid communication with the outlet port. The supply line is configured to deliver fluid to an exhaust component. A controller is configured to adjust pump flow rate to maintain a desired pressure in the supply line. A restriction is utilized in a return flow path from the supply line.

TECHNICAL FIELD

The subject invention relates to a control system to supply fluid to an exhaust component, and more particularly relates to a control system that adjusts pump flow rate to maintain a desired pressure in a supply line associated with the exhaust component.

BACKGROUND OF THE INVENTION

Vehicle exhaust systems can include a supply system that is configured to supply fluid, such as diesel fuel or urea for example, to an exhaust gas stream within an exhaust component. The supplied fluid is utilized within the exhaust component to initiate a desired reaction, or the fluid can be ignited or combusted by the hot exhaust gases to further increase the temperature within the exhaust component as needed.

Control systems for supplying the fluid utilize a pump to deliver the fluid to the exhaust component. Typically, a flow regulating valve is positioned downstream of a pump outlet to deliver the desired amount of fluid to the exhaust component. In one known system, a pressure regulating valve is positioned in a return flow path to the fluid supply. The pressure regulating valve opens when system pressure is too high, allowing fluid to return to the supply.

SUMMARY OF THE INVENTION

A control system for a pump includes a pump having an inlet port and an outlet port, a fluid supply in fluid communication with the inlet port, and a supply line in fluid communication with the outlet port. The supply line is configured to deliver fluid to an exhaust component. A controller is configured to adjust pump flow rate to maintain a desired pressure in the supply line.

In one example, a restriction is utilized in a return flow path from the supply line. The restriction comprises a fixed restriction having an opening defined by a fixed size. Fluid flows through the restriction any time the pump is active.

In one example, a pressure sensor measures pressure in the supply line and communicates this measured pressure to the controller. The controller adjusts the pump flow rate based on the measured pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a control system for a pump in a vehicle exhaust system.

FIG. 2 is a schematic view of one example of a restriction used in the control system of FIG. 1.

DETAILED DESCRIPTION

A vehicle exhaust system 10 is used to remove particulates from exhaust gases generated by an internal combustion engine 12. The vehicle exhaust system 10 is comprised of various combinations of exhaust components 14 as known. In one example, the exhaust system 10 includes one or more exhaust components 14 that utilize a fluid supply system 16. Fluid is supplied to an exhaust gas stream in the exhaust component 14 to produce a desired effect within the exhaust gas. Typically, an injector 18 is used to supply fluid to the exhaust component 14. In one example, the fluid is supplied to the exhaust stream to initiate a desired reaction. For example, the exhaust component 14 may comprise a selective catalytic reduction (SCR) component that is supplied with a urea-based fluid to reduce NOx emissions. In another example, the fluid is supplied to the exhaust stream for the purpose of increasing a temperature of the exhaust stream. For example, the exhaust component 14 may comprise a diesel particulate filter (DPF) that is supplied with fuel for regeneration purposes.

A control system 20 is used to meter the amount of fluid supplied to the exhaust system 10. The control system 20 and fluid supply system 16 can be used with any type of exhaust component that would utilize a supply of fluid to produce a desired effect within the exhaust gas stream. The fluid supply system 16 includes a pump 22 having an inlet port 24 at a suction side and an outlet port 26 at a pressure side. A fluid supply source 28 is in fluid communication with the inlet port 24. The fluid supply source 28 can be a separate dedicated supply source, or could be an existing fluid supply found within the vehicle. Examples of fluids for the fluid supply source 28 would be diesel fuel or urea; however, other types of fluids could also be used.

A supply line 30 is in fluid communication with the outlet port 26 and is configured to deliver fluid to one or more exhaust components 14. The control system 20 is configured to adjust a pump flow rate to maintain a desired pressure in the supply line 30. A return flow path 32 is configured to return fluid from the supply line 30 to the pump inlet port 24.

A restriction 34 is positioned within the return flow path 32. The restriction 34 is positioned upstream of the fluid supply source 28 and returns fluid to an inlet 36 to the supply source 28. The restriction 34 limits the flow rate of the fluid, which results in a higher pressure in the supply line 30 than if the fluid was not restricted. The restriction 34 comprises a fixed restriction, i.e. there is no variable fluid flow through the restriction. As such, fluid flows through the restriction 34 any time the pump 22 is active. Additional flow may also be metered to other devices or systems. The pump 22 includes a power source 38 that is used to run the pump 22 when activated by the control system 20.

In one example, the fixed restriction 34 comprises an orifice having an opening defined by a fixed dimension, as shown in FIG. 2. The size of the opening is determined based on system requirements, the type of exhaust component, pump size, etc. In the example shown in FIG. 2, the opening is circular and the fixed dimension is a diameter D1; however, openings having other shapes could also be used. The diameter D1 is less than a diameter D2 upstream of the restriction 34 and is less than a diameter D3 downstream of the restriction 34. Decreasing the diameter of the opening at D1 results in a corresponding increase in pressure in the supply line 30.

A pressure sensor 40 is located downstream of the pump outlet 26 and upstream of the restriction 34. The pressure sensor 40 measures pressure in the supply line 30 and communicates the measured pressure to the control system 20. The control system 20 includes a controller 42 that adjusts the pump flow rate in response to the measured pressure. The controller 42 can be a dedicated control unit or can be integrated as part of an existing control unit in the vehicle, such as an engine control unit for example. The controller 42 adjusts the pump flow rate by selectively adjusting pump speed to maintain the desired pressure in the supply line 30. In one example, the control system 20 utilizes pulse width modulation (PWM) for controlling the pump 22; however, other types of methods could also be used.

The restriction 34 limits a return flow rate to the pump 22 resulting in an increase in pressure in the supply line 30. The system is configured such that pressure achieved in the supply line 30 when the pump 22 is at a maximum flow rate is higher than the desired pressure. In one example, to account for a condition where the fluid is at a low viscosity and the pump is operating at a maximum speed, the pressure within the supply line 30 should be approximately 10% over the desired pressure.

As discussed above, the control system 20 actively adjusts the pump flow rate to maintain the pressure in the supply line 30, i.e. the pressure at the pump outlet 26, at a desired pressure level. The control system 20 adjusts this flow rate based on the measured pressure and the size of the restriction 34. In one example, the desired pressure level comprises a pressure range having a predetermined tolerance. For example, if the desired pressure is 150 psi, the controller can be programmed to adjust the pump flow rate to hold the pressure within 145-155 psi in the supply line 30.

Further, as the pressure of the fluid is known at all times, a fault code can be generated if the pressure exceeds a maximum limit or falls below a minimum limit. The fault code can be stored within memory in the control system and/or communicated to an operator or technician as needed.

The system comprises a re-circulating system where fluid is pumped through a return flow path with the pressure at the pump outlet being maintained within a certain tolerance. The flow rate of the pump is controlled/adjusted in combination with the return flow having a fixed, i.e. non-variable restriction. The system adjusts pump speed to maintain the pressure at the desired level based on the size of the restriction and the measured pressure at the pump outlet. Additional non-recirculating flow could also be metered from this pressure-regulated fluid. The advantage with this system is that there is no need for a mechanical pressure regulator such as a spring-loaded valve, for example. As discussed above, the fluid supply could be a separate or dedicated fluid supply for injecting fluid into the exhaust component, such as a urea tank or a vehicle fuel tank for example.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. A control system for a pump comprising: a pump having an inlet port and an outlet port; a fluid supply in fluid communication with said inlet port; a supply line in fluid communication with said outlet port, said supply line configured to deliver fluid to an exhaust component; and a controller configured to adjust a pump flow rate to maintain a desired pressure in said supply line.
 2. The control system according to claim 1 including a return flow path configured to return fluid from said supply line to said pump, and including a restriction positioned within said return flow path.
 3. The control system according to claim 2 wherein said restriction is positioned upstream of said fluid supply.
 4. The control system according to claim 2 wherein said restriction comprises a fixed restriction.
 5. The control system according to claim 4 wherein said fixed restriction comprises an orifice having an opening defined by a fixed size.
 6. The control system according to claim 2 wherein fluid flows through said restriction any time said pump is active.
 7. The control system according to claim 2 including a pressure sensor downstream of said pump outlet and upstream of said restriction, said pressure sensor measuring pressure in said supply line and communicating measured pressure to said controller.
 8. The control system according to claim 7 wherein said controller adjusts said pump flow rate in response to said measured pressure.
 9. The control system according to claim 8 wherein said controller adjusts said pump flow rate by selectively adjusting pump speed to maintain said desired pressure.
 10. The control system according to claim 2 wherein said restriction limits a return flow rate to said pump resulting in an increase in pressure in said supply line, and wherein a pressure achieved in said supply line when said pump is at a maximum flow rate is higher than said desired pressure.
 11. A fluid supply control system for a vehicle exhaust system comprising: a pump having an inlet port and an outlet port; a fluid supply in fluid communication with said inlet port; a supply line in fluid communication with said outlet port, said supply line configured to deliver fluid to an exhaust component; a pressure sensor configured to measure pressure in said supply line and generate a measured pressure signal; a return flow path configured to return fluid from said supply line to said pump; a fixed restriction positioned within said return flow path; and a controller configured to adjust a pump flow rate to maintain a desired pressure in the supply line based on said measured pressure signal.
 12. The fluid supply control system according to claim 11 wherein said supply line supplies fluid to an injector that injects fluid into an exhaust gas stream within said exhaust component.
 13. The fluid supply control system according to claim 11 wherein said fixed restriction comprises an orifice having an opening defined by a fixed size, and wherein fluid flows through said orifice any time said pump is powered.
 14. The fluid supply control system according to claim 11 wherein said exhaust component comprises one of a SCR component or DPF component.
 15. A method of controlling a pump in a vehicle exhaust system comprising: providing fluid from a fluid supply to a pump inlet; pumping fluid into a supply line via a pump outlet; supplying fluid from the supply line to a vehicle exhaust component; and adjusting a pump flow rate to maintain a desired pressure in the supply line.
 16. The method according to claim 15 including restricting return flow to said pump to increase pressure in said supply line.
 17. The method according to claim 16 including configuring a restriction in a return flow path to have an opening defined by a fixed size.
 18. The method according to claim 17 including configuring the restriction such that fluid flows through the return path any time the pump is activated. 